The drugs clearly help patients who have already had a heart attack. But their use has skyrocketed in patients hoping to prevent a first heart attack. In those cases, the benefits are dubious.

As the world's most-prescribed class of medications, statins indisputably qualify for the commercial distinction of "blockbuster." About 24 million Americans take the drugs — marketed under such commercial names as Pravachol, Mevacor, Lipitor, Zocor and Crestor — largely to stave off heart attacks and strokes.

At the zenith of their profitability, these medications raked in $26.2 billion a year for their manufacturers. The introduction in recent years of cheaper generic versions may have begun to cut into sales revenues for the brand-name drugs that came first to the market, but better prices have only fueled the medications' use: In 2009, U.S. patients filled 201.4 million prescriptions for statins, according to IMS Health, which tracks prescription drug trends. That's nearly double the number of prescriptions written for statins in 2001, four years after they arrived on the American pharmaceutical landscape.

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